Research on the communication and academic achievement of children receiving cochlear implants (Cl) shows that these children become functional members of the hearing community alongside other children with less severe hearing loss who wear hearing aids (HAs). The extent to which children with CIs have similar functional capabilities will be addressed in this research program. We will obtain data on non-speech auditory perception, speech perception, music perception, speech, language, reading skills and service provision for a group of 7 and 8 year old children fitted with unilateral, bimodal or bilateral CIs. These data will be compared qualitatively and quantitatively with mild to severe hard of hearing (HH) age mates. This aim will lead to evidence-based clinical guidelines in determining candidacy criteria for cochlear implants or hearing aids. Recently, CIs that preserve residual acoustic hearing (hybrid devices) have been shown to provide hearing benefits to adults with some residual hearing but, these devices have not yet been used with children. In this study, children who are 5 to 15 years of age with moderate to severe hearing loss will receive a hybrid cochlear implant. Speech perception, speech production, language, music perception outcomes will be compared to bimodal and HH children. This aim explores an alternative for children who have some residual hearing, but are not benefitting from conventional hearing aids, to simultaneously take advantage of electric stimulation and their natural acoustic hearing. Aim 3 evaluates the feasibility implanting children with profound deafness with a short electrode in one ear and a standard-length electrode in the other ear. The purpose is an attempt to preserve regions of the cochlear partition future medical interventions in the ear with the short electrode. A within-subject design will evaluate equivalency between the ear with the short electrode array and the ear with the standard-length array on speech perception and electrophysiological measures.